Instrument for detecting electric oscillations.



J. A. FLEMING.

INSTRUMENT FOR DETECTING ELECTRIC OSGILLATIONS.

APPLICATION FILED JAN.2, 1909.

954,61 9, Patented Apr. 12, 1910.

(Ya [I {I I (/5/1 I! (YmbmspFlemmy u I D STATES PATENT OFFICE.

afomr'mnnosnrnsmnsi oftemon, ENGLAND, na e rommcom wrmnss new messy.

INSTRUMENT FOR DETECTING ELECTRIC OSQ ILLATIOIIS.

application filed January 5,1909. s riainonu'oaga To' all whom it mayconcern:

Be it known that I, J 01am AMBRosE FLEM- of lege, Gower Street, in thecounty of London, England, have invented new and useful Imrovements inInstruments for Detecting lectric Oscillations, of which the followingis a specification.

My invention has reference to that type of electricaloscillationdetector described by me in the United States patentspecification No. 808684 dated 7th November 1905.

In this specification I described an oscillation detector subsequentlycalled an oscillation 'valve or glow lampdetector, which consists of anelectric glow lam of the ordinary type, but having within t e glassbulba metal plate or cylinder carried on an insulated terminal sealedthrough the glass. When-the filament is rendered incandescent by anelectric current, it emits negative ions or corpuscles or electrons andthese ionize the residual gas in the bulb, and give to the space aunilateral conductivity by which negative electricity can pass from thehot filament to the cold insulated plate or cylinder within the bulb,but not in the opposite direction. I employed this device as an electricwave detector in radiotelegraphy by connecting the insulated plate orcylinder to one terminal of an oscillation transformer inserted in thereceiving circuit of the radiotelegraphic apparatus, and the otherterminal of this oscillation transformer was connected through agalvanometer or telephone to the negative terminal of the filament. 7

I have discovered after many ex eriments that tungsten in various formsan particularly a form in which it is employed as the filament in a glowlamp is highly e cient for this purpose since the amount of negative.

ms doctor of science a subject of the King ireat Britain, resi ing atUniversity Col- I specification 01!LettersIkatent. Patented Apr,-

they can be worked in ractice. I have also discovered that a cylinder ofcarbon acts better-as the cold conductor in the bulb than the metalliccylinders heretofore employed.

" perior tocarbon at-any temperature at which I construct such ametallic or semi-metallic filament glow lamp with a tubular glass bulband a cyhnder of carbon sealed into the bulb,

and connected to a platinum"wire sealed throu h the glass. "Furthermore,I employ .this g ow lamp as an oscillation detector as follows :The'filament is rendered incandescent by an insulated battery having inseries with it a rheostat or variable resistsurrounding but not touchingth m K ance for controlling the current. Across the terminals of thisbattery -I place another high resistance having a sliding contact in it,so as to make contact with any desired point on this resistance.

In using this detector in wireless teleg- 7 raphy the receiving circuitmust comprise a closed circuit having inductance and containing acondenser. If the telegraphy is conducted by electric waves it isnecessary also to connect an antenna either directly ,or indirectly withthis condenser circuit. I

then connect the insulated cylinder included within the bulb of the lampwith one plate of the condenser in the oscillation circuit, and Iconnect the othenplate of this 5 condenser with the sliding contact onthe re sistance across the glow lam battery terminals. In this circuit Ialso include a telephone or current detecting instrument. A

the filament rendering it incandescent, and also in virtue ofthe-emissionof negative electricity from the filament a current flowsfrom it through the vacuous space to the metal cylinder and through thetelephone or I other current detector. The conductivity of this vacuousspace or ionized rarefied gas is a function of the electromotive forceacting to drive the current through it. I find that if the position ofthe sliding contact on the resistance across the terminals of thebattery is so adjusted that corresponding thereto the conductivity curveof the ionized gas has a very sudden change in curvature,

the superppsition of an oscillatory potential difiere'nce between thefilament and cylinder upon the steady potential diflerence causes I verysudden changes in the current strength current then flows from thebattery through 90 I electric waves or magneto electric induction tion Iplace across the termina intelligence to a distance.

In the drawing accompanying and forming a part of this specification, Ihave illustrated one embodiment of my invention. Referring to thisdrawing it will be seen that in carrying my invention into efiect Iemploy a tubular form of glass bulbca which may be an inch or more indiameter and five or six inches in length. In this I insert a cylinder bof carbon which is sprung into the glass tube so as to fit the wallstightly. This cylinder has a platinum wire a twisted or welded to itwhich is sealed through the glass, so as to make an external electricalconnection. The bulb a should have a good vacuum such as is usuallyemployed with lamps having metallic filaments.

The metallic filament d is formed of tung-.

sten in the form used as a filament in ordi-' nary glow lamps and isconnected to conductors 6 carried on a lass tubular stem 7 sealed intothe bulb. T e filament (1 should be of such a length that it is entirelycovered by the metal cylinder 6. It is convenient to have the filamentof such length and thickness that the voltage required to bring it toincandescence at which its durationmay not be less than several hundredhours, is of the order of 18 volts or so.

In applying this glow lamp as a detector in radiotelegraphyl arrange itas follows A battery 9 o seconda cells is provided which mayconveniently e a dozen or more cells, and wires h are brought from theterminals of thisbattery to the terminals e of the filament of the lamp,a variable resistance j'k being inserted in the circuit. It isconvenient to divide this resistance into two,

one namely of from say 0 to. 120 ohms be-- ing for coarse adjustment andthe other is of from sa O'to 5 ohms being for fine adjustment. means ofthese resistances the current of the lamp ma be adjusted to have anyrequired value. X voltmeter I should also be placed across theterminalsof the filament to regulate the volta e. In addiof the batteryg a high resistance m of the potenti: ometer type, that is to say, aresistance which may be two or three hundred ohms or more, the terminalsof which are connected 'serted in a circuit possessing in to theterminals hot the batter A double high resistance telephone 12. (t efresistance of each telephone being at least five or six hundred ohms)has one terminal connected to a slider 0 which can make contact with anyrequired point on the resistance m and the other terminal connected toone late of a condenser 32. The other plate of t e condenser p isconnected with the metal cylinder of the lamp. The condenser isindiictance, which is directly or inductively connected with a receivingantenna. As shown thecircuit connecting the two plates of the condenserp contains an adjustable -1nductance g and the secondary of the jigger rthe primary of which is in the aerial .9. When electric waves fall uponthe receiving antenna they excite oscillations in the condenser circuitand oscillations are thus imposed upon the telephone circuit connectinthe metal cylinder or plate in the lamp with the sliding contact andhigh resistanceconnected across the terminals of the battery or othersource of continuous electric current.

In operating the arrangement, the first step is to bring the filament toa high incandescence at which it would be working a proximately at onewatt per candle and at w liich it will have such a temperature,approximately 2800 0., that it will diffuse into the vacuous spacenegative ions discharged from the incandescent filament. The filamenthaving been rendered incandescent to this temperature,fthe observerapplies the telephone to his ear and if electric wave trains are fallingu on the receiving antenna 8, it'will be foun that on moving the slider0 along the potentiometer resistance m from one end to the other, thereis a certain point at which sounds will be heard in the telephone betterthan at any other point. The exact osition of the slider 0 must bedetermine by trial for it varies with every valve owing to slightdilferences in the vacuum and temperature of the filament. The detectorabove described is suitable as the receiver in radiotelephony, as wellas for signals on the Morse or other a1 habetic code.

- atIclaim-is:-

1. A rectifienor valve for electric oscillations, having one electrodecomposed of tungsten.

2. A rectifier or valve for electric oscillations, having one electrodecomposed of tgungsten and one element composed of car- 3. A rectifier orvalve for electric oscillations, comprising a metallic filamentconstituting one electrode, means for heating said filament, and a plateofcarbon constituting another electrode thereof.

4. A rectifier 0r valve for electric oscilla tions, comprising a.metallic filament constiloo tuting one electrode, means for heating saidfilament, and a curved plate of carbon circumferentially situated. inrelation to the longitudinal axis of said filament.

5. An oscillation valve in which the hot conductor is a filament oftungsten.

6. An oscillation valve com rising a heated electrode in combinationwith a cold electrode consisting of a mass of carbon.

7. An oscillation valve comprising a heated electrode in combination:with a cold electrode consisting of a cylinder of carbon.

8. An oscillation valve in which the hot conductor is a filamentoftungsten and the cold conductor is a cylinder of carbon.

9. The combination of an oscillation valve, a source of electricityheating the filament of the valve, a resistance across the terminals ofthe source, a circuit connected atone end to the cold conductor of thevalve and 10. In combination with an oscillation valve, a source ofelectric current for energizing the filament thereof, an oscillatory 1circuit having one terminal connected wit one element of saidoscillation valve, the other terminal of said oscillatory circuit be-.ing adjustably connected With a resistance hich is connected with oposlte terminals of another element of sai valve, and a translatingdevice operatively connected with said circuits for indicating thepresence of electric oscillations. 4

JOHN AMBROSE FLEMING. Witnesses:

Gno. J. B. FRANKLIN, I T. J. OSMAN.

